(i) Field of the Invention
This invention relates to an air inflatable mattress, a method for its manufacture and apparatus for use in the manufacture; more especially the invention is concerned with air inflatable mattresses for medical or hospital use.
(ii) Description of the Prior Art
Air mattresses have been proposed for medical and hospital use, for example to minimize development of bed sores and to support patients who have suffered from extensive burns.
In such mattresses it would be advantageous to have the supporting force of the internal pressurized air distributed uniformly beneath the support surface, and to so construct the mattress that deflating external force applied to one part of the support surface does not unduly affect the internal air pressure exerted on the support surface of other parts of the air mattress.
Previous proposals for air mattresses have been relatively complex. One prior proposal employs a plurality of discrete, inflatable members assembled together, each with a pressurized air supply as in Canadian Patent 1,077,173, L. A. Hopkins, issued May 6, 1980. Another prior proposal requires a complex mandrel which is coated with a film forming material to form a plurality of air inflatable cells, as in Canadian Patent 1,044,823, R. H. Graebe, issued Dec. 19, 1978.
U.S. Pat. No. 4,149,285, A. N. Stanton, issued Apr. 17, 1979, proposes an air mattress with elastic upper and lower support walls interconnected at a multiplicity of points by internal flexible ties that restrain separation of the support walls. U.S. Pat. No. 4,528,704, J. Wegener, issued July 16, 1985, employs top, intermediate and bottom flexible sheets as well as a semi-rigid backing; the top and intermediate sheets form high pressure tubes.